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Thu, 18 Apr 2024 12:31:30 -0700 (PDT) Received: from smtpclient.apple ([132.69.239.36]) by smtp.gmail.com with ESMTPSA id c26-20020a170906d19a00b00a55662919c1sm1277105ejz.172.2024.04.18.12.31.27 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Thu, 18 Apr 2024 12:31:30 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3774.500.171.1.1\)) Subject: Re: [RFC PATCH 3/7] module: [ From: Nadav Amit In-Reply-To: Date: Thu, 18 Apr 2024 22:31:16 +0300 Cc: Linux Kernel Mailing List , Andrew Morton , Andy Lutomirski , Arnd Bergmann , Catalin Marinas , Christoph Hellwig , Helge Deller , Lorenzo Stoakes , Luis Chamberlain , Mark Rutland , Masami Hiramatsu , Mathieu Desnoyers , Michael Ellerman , Palmer Dabbelt , Peter Zijlstra , Russell King , Song Liu , Steven Rostedt , Thomas Gleixner , Uladzislau Rezki , Will Deacon , bpf , linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org, "open list:MEMORY MANAGEMENT" , linux-modules@vger.kernel.org, linux-parisc@vger.kernel.org, linux-riscv@lists.infradead.org, linux-trace-kernel@vger.kernel.org, linuxppc-dev , the arch/x86 maintainers Content-Transfer-Encoding: quoted-printable Message-Id: References: <20240411160526.2093408-1-rppt@kernel.org> <20240411160526.2093408-4-rppt@kernel.org> <0C4B9C1A-97DE-4798-8256-158369AF42A4@gmail.com> To: Mike Rapoport X-Mailer: Apple Mail (2.3774.500.171.1.1) X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 0DCCF2000D X-Rspam-User: X-Stat-Signature: 4ptn4grewzyikyesf6zhb5jwaa7i3md3 X-HE-Tag: 1713468692-169650 X-HE-Meta: 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 MOD4gZCG 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: > On 18 Apr 2024, at 13:20, Mike Rapoport wrote: >=20 > On Tue, Apr 16, 2024 at 12:36:08PM +0300, Nadav Amit wrote: >>=20 >>=20 >>=20 >> I might be missing something, but it seems a bit racy. >>=20 >> IIUC, module_finalize() calls alternatives_smp_module_add(). At this >> point, since you don=E2=80=99t hold the text_mutex, some might do = text_poke(), >> e.g., by enabling/disabling static-key, and the update would be >> overwritten. No? >=20 > Right :( > Even worse, for UP case alternatives_smp_unlock() will "patch" still = empty > area. >=20 > So I'm thinking about calling alternatives_smp_module_add() from an > additional callback after the execmem_update_copy(). >=20 > Does it make sense to you? Going over the code again - I might have just been wrong: I confused the alternatives and the jump-label mechanisms (as they do share a lot of code and characteristics). The jump-labels are updated when prepare_coming_module() is called, = which happens after post_relocation() [which means they would be updated using text_poke() =E2=80=9Cinefficiently=E2=80=9D but should be safe]. The =E2=80=9Calternatives=E2=80=9D appear only to use text_poke() (in = contrast for text_poke_early()) from very specific few flows, e.g.,=20 common_cpu_up() -> alternatives_enable_smp(). Are those flows pose a problem after boot? Anyhow, sorry for the noise.=